In a magnetic field based non-contact current sensor, current through a low-resistance metal trace creates a magnetic field that is sensed by a magnetic sensor. The intensity of the created magnetic field may be proportional to the current flowing through the trace. There are many types of magnetometers that may be used for measuring a magnetic field; see, e.g. “Magnetometer”, Wikipedia, as of Dec. 7, 2015. One type of magnetometer that is commonly used for current sensing applications is a Hall device.
Another magnetometer that is commonly used for current sensing applications is the fluxgate magnetometer. Fluxgate magnetometers (FGM) were invented in the 1930s by Victor Vacquier at Gulf Research Laboratories. A fluxgate magnetometer consists of a small, magnetically susceptible core wrapped by two coils of wire. An alternating electric current is passed through one coil, driving the core through an alternating cycle of magnetic saturation; i.e., magnetized, unmagnetized, inversely magnetized, unmagnetized, magnetized, and so forth. This constantly changing field induces an electric current in the second coil, and this output current is measured by a detector. In a magnetically neutral background, the input and output currents will match. However, when the core is exposed to a background field, it will be more easily saturated in alignment with that field and less easily saturated in opposition to it. Hence the alternating magnetic field, and the induced output current, will be out of step with the input current. The extent to which this is the case will depend on the strength of the background magnetic field. The current in the output coil may be integrated over a period of time to yield an analog voltage proportional to the magnetic field.
Other features of the present embodiments will be apparent from the accompanying drawings and from the detailed description that follows.